On Tue, 2008-12-02 at 13:18 +0900, Tejun Heo wrote: > Nicholas A. Bellinger wrote: > >>> So far during my initial testing, I am running into a two different > >>> exceptions. One NULL pointer deference OOPS after half dozen Open/iSCSI > >>> login/logouts in block/elevator.c:elv_dequeue_request(). Here is the > >>> trace from SCSI softirq context: > >>> > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-0.png > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-1.png > > Can you build with debug info and find out which line is the offending > one? (gdb) list *(elv_dequeue_request+0x1d) 0x1320 is in elv_dequeue_request (include/linux/list.h:92). 87 * This is only for internal list manipulation where we know 88 * the prev/next entries already! 89 */ 90 static inline void __list_del(struct list_head * prev, struct list_head * next) 91 { 92 next->prev = prev; 93 prev->next = next; 94 } 95 96 /** (gdb) list *(elv_dequeue_request+0x19) 0x131c is in elv_dequeue_request (block/elevator.c:836). 831 EXPORT_SYMBOL(elv_next_request); 832 833 void elv_dequeue_request(struct request_queue *q, struct request *rq) 834 { 835 BUG_ON(list_empty(&rq->queuelist)); 836 BUG_ON(ELV_ON_HASH(rq)); 837 838 list_del_init(&rq->queuelist); 839 840 /* > > >>> The other one is a BUG_ON in blk/blk-timeout.c:177 in blk_add_timeout() > >>> that happens after a few hundred MB of READ_10 traffic, which also > >>> appears to pass through elv_dequeue_request() at some point: > >>> > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-2.png > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-4.png > > Hmmm... this means blk_add_timer() is being called after the request > is already completed. All the problem discovered till now have to do > with timeout going off without the low level driver knowing about the > request. I don't have much idea and it'll probably be best to trace > what's going on using blktrace or printks. <nod>, OK. > Maybe this is caused by > list corruption as with the first issue or request completion races > with requeueing? Hrmm, yeah, perhaps the use of scsi_req_map_sg() (which obviously still has struct bio behind it) is causing the breakage.. I will wait for Tomo, Boaz and co to have a look at the original patch to lio-core-2.6.git/drivers/lio-core/target_core_pscsi.c and see if I am missing something obvious. Also, with the previous patch to drivers/scsi/scsi_lib.c(), I am able to move a few GB of bulk I/O and not hit the BUG_ON in blk/blk-timeout.c:177 in blk_add_timeout() mentioned above when feeding struct request into struct scsi_device->request_queue with blk_execute_rq_nowait() with use_sg > 0 CDBs. However, I am still running into another reproducable BUG_ON in block/cfq-iosched.c:cfq_find_next_rq() after extended bulk I/O tests. Many thanks for your comments, --nab > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
